“You have all heard that Nature abhors a vacuum. Such at least is the nature of the heart, that though the room which is in it may change one inmate for another, it cannot be left void without the pain of most intolerable suffering. It is not enough then to argue the folly of an existing affection. It is not enough, in the terms of a forcible or an affecting demonstration, to make good the evanescence of its object.
It may not even be enough to associate the threats and the terrors of some coming vengeance, with the indulgence of it. The heart may still resist the every application, by obedience to which, it would finally be conducted to a state so much at war with all its appetites as that of downright inanition. So to tear away an affection from the heart, as to leave it bare of all its regards and of all its preferences, were a hard and hopeless undertaking – and it would appear, as if the alone powerful engine of dispossession were to bring the mastery of another affection to bear upon it.”
Thomas Chalmers, The Expulsive Power of a New Affection (PDF here)